Water level sensors are used in fuel filters in order to detect, with regard to its quantity, and to temporarily discharge the water which is continuously separated from the fuel. Such water level sensors are usually arranged here in water accumulators and report a water level, which is present there, continuously or cyclically to a control device, which on reaching of a predefined level generates a signal and, for example, discharges the water which has collected in the water accumulator.
Usually, the water level sensors which are used for this are configured as plastic injection moulded parts with electrically conducting poles, wherein via the electrically conducting poles and the water, an electrically conducting connection can be created, which informs via the water level present respectively in the water accumulator. The electrically conducting poles can be configured here for example in the manner of lines, wherein increasingly also electrically conducting plastics are being used, which have, for example, electrically conducting fibres, such as in particular carbon fibres.
When water level sensors are produced here by a conventional plastic injection moulding process, then a smooth surface in the plastic injection mould or respectively in the injection moulding tool produces a so-called injection skin, because the fibres arranged in the injected plastic are aligned substantially parallel to the wall surface of the plastic injection mould. The produced injection skin has, however, an insulating effect with respect to the remaining plastic material with the corresponding fibre content, because during the injection moulding process no more fibres are present on the surface, or only a reduced fibre content. Hereby, the electrical conductivity on the surface of the water level sensor is negatively impaired, which can lead to difficulties in particular with an electrical connecting to another component.